Wash and dry all produce. Adjust rack to upper position and preheat oven to 450 degrees. Cut chicken into 1/2-inch cubes, then toss in a medium bowl with 5 tsp Southwest spice (we’ll use the rest later).

Heat a large drizzle of olive oil in a large pan over medium-high heat (use a nonstick pan if you have one). Add chicken and cook, tossing occasionally, until lightly browned, 4-5 minutes. Meanwhile, halve, core, and seed bell peppers, then cut into 1/2-inch squares. Trim, then thinly slice scallions, reserving 1 TBSP greens for garnish.

Add bell peppers and remaining scallions to pan with chicken. Season with salt and pepper. Cook, stirring occasionally, until peppers are slightly softened, about 2 minutes. Stir in enchilada sauce and 1/2 cup water. Let simmer gently until sauce is slightly thickened and warmed through, about 3 minutes.

Lightly oil a baking dish (we used an 8- by 10-inch dish). Lay 3 tortillas on bottom, covering as much surface area as you can. Using a slotted spoon, spread chicken and bell peppers evenly over tortillas, leaving most of the sauce in pan. Lay remaining tortillas on top, then pour over sauce from pan. Sprinkle with cheese. Bake in oven until cheese melts and is lightly browned, 10-12 minutes.

Meanwhile, zest 1 tsp zest from lime, then cut lime into wedges. In a small bowl, stir together lime zest, remaining Southwest spice, and sour cream. Season with salt and pepper.

Let casserole rest 5 minutes after removing from oven. Divide between plates. Dollop with crema and garnish with reserved scallion greens.